In addition to the standard set of driver functions for the control/driver circuitry for controlling the switching times of the output MOSFETs of a DC-DC converter, there are two additional functions that may be desired for some applications. A first of these functions is the ability to control the mode of operation of the driver as either forced continuous conduction mode (FCCM) or discontinuous conduction mode (DCM). This is largely desired in portable power supply applications, and is usually implemented by applying a digital signal to a logic input pin of the IC, the logical state of the digital signal designating the mode of operation. A second function is to allow for programming of the dead-time between the switching of the output MOSFETs, which is important for optimizing switching performance over a wide selection of the power devices.
In today's driver IC market, an eight-pin SOIC package is one of the most popular for half-bridge driver implementations. Unfortunately, an eight pin package means that only a single pin is available for auxiliary functions, such as the two control/programming functions mentioned above, since the other seven pins are already taken for the basic operation of the driver IC. The problem is how to enable both of the above functions to be supplied to the driver IC by means of the one available pin.